Usage of expressions and contexts in uses clause

[kellervater]

I’ve got a use case where I want to test my action in an example workflow.
This works out great for me with hardcoded values in the uses clause. But it would be much more elegant to be able to use context variables like github.repository in the uses clause to be fork agnostic.

Something like this:

...
        uses: "${{ github.repository }}@master"
...

In my case I test a fork of a Github Repo. This means the root of my fork has another repository name than I do.
So it’ll be great if this repository could be resolved dynamically by using the github context.

This is currently not possible and ends with:

### ERRORED 11:55:40Z

Your workflow file was invalid: The pipeline is not valid. .github/workflows/gpr.yaml (Line: 14, Col: 13): Unrecognized named-value: 'github'. Located at position 1 within expression: github.repository

[wipe2238]

You can use path as argument for uses, so this should do the trick

- uses: ./

[kellervater]

Thank you very much. This did the trick. Kudos to you 😃

[chrispat]

For a bit more color.  Because we have the settings where a repo or org owner can specify if they want third party actions or not we need to be able to resolve the full list of referenced actions before we start the workflow.  If we enabled expressions in the uses section that would not be possible until runtime and we would potentially get hours into a job before it failed due to this policy.

[krebemm]

how would you use this expression with both dynamic and static variables?

[jenseng]

By static do you mean a hardcoded value? Within expressions, you can use literal strings. For example, this expression hardcodes the v1 tag if we're in another repo:

${{ github.repo == 'SameOrg/same_repo' && github.sha || 'v1' }}

[krebemm]

yes, hard coded. i was thinking something like:

${{ github.repo == 'SameOrg/same_repo' && 'static value here'github.sha || 'v1' }}

but i actually just found a fix by just adding it outside of the expression like
'static value here' ${{ github.repo == 'SameOrg/same_repo' && github.sha || 'v1' }}

[jenseng]

When I need to mix dynamic and static stuff in expressions, another useful thing i've found is the format function, e.g.

${{ github.repo == 'SameOrg/same_repo' && format('static value here{0}', github.sha) || 'v1' }}

[krebemm]

awesome! thank you for the syntax

[kellervater]

Thank you for this explanation

[eps1lon]

Do you have a working example for this? When I tried this it was not doing anything: https://github.com/eps1lon/actions-label-merge-conflict/blob/2f617ca50dfb880adbf628a61e3d4f427561a1df/.github/workflows/ci.yml#L24

[atoomic]

This works fine for me if you have an action.yml in your root directory

- uses: actions/checkout@v2
- uses: ./

[mktcode]

@wipe2238 The link to the docs seems to be outdated.

https://docs.github.com/en/actions/reference/workflow-syntax-for-github-actions#example-using-an-action-in-the-same-repository-as-the-workflow

[jenseng]

You can work around this with nested composite actions; although the job step's uses need to be static/resolvable, if one of those actions is a composite action, its own uses won't be resolved until the action runs. So we can use this to our advantage to dynamically build a composite action that runs our desired action. It's a tad convoluted, so I made a generic action to make this a little more sane 😅

Given a step like so:

- uses: actions/setup-node@v3
  with:
    node-version: 18

If you want your uses to be dynamic you can do:

- uses: jenseng/dynamic-uses@v1
  with:
    # now you can use expressions 🥳
    uses: actions/setup-node@${{ inputs.version }}
    # the `with` needs to be converted to a valid json string
    with: '{ "node-version": 18 }'